The present invention relates to a method for preparing 3-benzazocine derivatives, more particularly, to a method for preparing 8-acylthio-1,2,3,4,5,6-hexahydro-2,6-methano-3,6(e),11(a)-trimethyl-3-benz azocines represented by general formula (I) ##STR3## wherein R represents an alkyl group, a phenyl group or a heterocyclic group from 1,2,3,4,5,6-hexahydro-2,6-methano-3,6(e),11(a)-trimethyl-3-benzazocine represented by the formula (II) ##STR4##
It is known that the type of compounds represented by general formula (I) are analgesic compounds which are non-addictional and can show pharmacological effects by oral administration as described in Japanese patent applications (OPI) Nos. 124281/1978, 61181/1979 and 13253/1980.
In the above published applications there are described the following synthetic pathways. ##STR5##
However, these methods for preparing benzazocine derivatives are disadvantageous in that narcotic compounds represented by the formula (2) must be used as a starting material and the methods comprise many steps.